This invention relates to a shaving aid strip (or composite) for a razor cartridge.
It is now well known that shaving comfort can be enhanced by affixing to a razor cartridge a shaving aid composite, also known as a lubricating strip, which continuously releases a shaving aid, typically a lubricant, during the shaving process. See, for example, U.S. Pat. No. 4,170,821 and GB 2,024,082. The shaving aid strip generally comprises a water-insoluble polymer matrix, typically polystyrene, and a water-soluble shaving aid, typically polyethylene oxide, which leaches out of the composite during shaving to enhance shave comfort.
Unfortunately, conventional shaving aid strips suffer from the disadvantage that they release an insufficient amount of the shaving aid, particularly after the first four or five shaves where release of the shaving aid may drop off to negligible quantities. In addition, the amount of shaving aid that may be included in the shaving aid strip may be limited because high levels of shaving aid are difficult to process and can adversely affect the structural integrity of the strip. Accordingly, recent efforts have been made to improve shaving aid strips so as to enhance and prolong release of the shaving aid.
Such efforts have resulted in improved shaving aid strips which include the following features: incorporation of a low molecular weight release enhancing agent, such as polyethylene glycol, into the matrix (U.S. Pat. No. 5,113,585); the use of ethylene vinyl acetate copolymer as the matrix material (U.S. Pat. No. 5,349,750); incorporation of a compatibilizer material such as polyethylene oxide-polypropylene oxide copolymer (e.g. Poloxamer 182) (U.S. Pat. No. 5,454,164); incorporation of a water-swellable polymer such as Salsorb 84, a cross-linked polyacrylic (U.S. Pat. No. 5,626,154); coextrusion of a core comprising a water-leachable shaving aid within a sheath of water-insoluble polymer, wherein the sheath has a plurality of openings to facilitate release of the shaving aid (WO 96/13360, which corresponds to U.S. Ser. No. 08/497,194); and coextrusion of adjacent shaving aid portions (U.S. Pat. No. 5,956,848). Also known are shaving aid strips which include an essential oil (U.S. Pat. No. 5,095,619) or a non-volatile cooling agent (U.S. Pat. No. 5,713,131), and injection molded strips which include a plasticizer (U.S. Pat. No. 4,850,106). All of the aforementioned patents or published applications are incorporated herein by reference.